Electric discharge tube and seal therefor



' Aug. 9, 1949.

E. G. DORGELO ET AL ELECTRIC DISCHARGE TUBE AND SEAL THEREFOR Filed May 2, 1946 ATTORNEY.

Patented Aug. 9, 1949 ELECTRIC DISCHARGE TUBE AND SEAL THEREFOR Eduard Gerardus Dorgelo and. Hendricus Johannes Lemmens, Eindhoven, Netherlands, assignors, by mesne assignments, to Hartford National Bank and Trust Com pany, Hartford, Conn, as'trustee Application May 2, 1946, Serial No. 666,569' In the Netherlands. November '14, 1940 Section 1, Public Law 690, August 8, 1946.

Patent expires Novemberl4, 1960 3 Claims. l;

The invention grelates .to a device comprising an :electric discharge tube, more particularly for amplifying orgenerating; electrical oscillations of very high frequency. The invention furthermore relates to ia tubersuitable for being utilized in such a device.

One of the most-important problems which arisein the construction .of tubes and devices it has been endeavoured indifferent ways to make the connectionsreferred'to as short as possible in order to be ableto utilize these apparatus for veryshort waves." Thus: for example, it has been proposedxto formrtwoelectrodes of a discharge tube themselves'withinthe tube as an oscillatory circuit; itlisalsoknown to connect 11$ or to couple theelectrodes either-directly or capacitatively with; conductors present outside the tube, in which event :theseconductors form an oscillatory circuitand; when .directly connected to the electrodes, mayact. at the sametime as current supply conductors.

These known tubes and devices have several drawbacks; if the-oscillatory circuit. is formed by'the electrodes themselves and is located exclusively within the tube,- it is impossible directly to-alter the'lengthpf theoscillatory circuit at will and thus.tormodify'thewave-range. If the electrodesare; connected toconductors located outside the tube, we encounter the drawback that seals are necessary and that it is not simple to utilize .continuous. conductors which consist of one piece.

It has been proposed to seal the cathode body of an indirectly heated cathodeand the supporting membersof thesrid and the anode as such into a pinch bat. The latter construction required comparatively thin conductors. With the pinches and othermembers'for sealing a discharge tube which were known up to ashort time ago, it was impossible directly to seal-in conductors of such thickness that they could act at the same time as constituent parts of an oscillatory circuit.

In a prior patent application the applicant has proposed to seal current supply conductors for electric apparatus, for example for electric discharge tubes, into a body which has a vacuumtight structure which consists, to the extent of at least 5%, of finely divided cavities and has a specific weight which is at least 5% lower than 2 that of the. glass present in this body in homogeneous. and substantially air or gas free condition. As described. in this prior specification, it is thus possible to seal to one another widely different combinations of glass and metal whilst, in addition, a simplification in the manufacture of discharge tubes may be obtained owing to the fact that the electrodes and the supply conductors can at first beb-roughtinto their final '3 position and then may be sealed together, if desired, also simultaneously With.the bulb.

Building further thereon the applicant has found it to be possible to work out a device and a discharge tube which are particularly suitable for short-wave purposesand. withthe aid of which the disadvantages. set out hereinbefore may be avoided.

A device according to the invention comprises to that end a tube which. is closed at at least one end by a member which exhibits a vacuum tight structure which. consists, to the extent of at least 5%, of finely divided cavities filled with air or gas, andhas a specific weight which is at least 5% lower than that of the-glass present in this member in a homogeneous-and substantially airor gas free condition and wherein one or more electrodes or parts thereof are sealed as such into the sealing memberand are continued outside the tube and .-form there at the same time the constituent parts of an oscillatory circuit. With the expression electrode parts we must thinl; in the first place of the supporting members of the grids or anodes.

With the use'of' the above-described device the electrodes and the constituent parts of the oscillatory circuit consist of the same material and, owing to the fact that conductors of any desired diameter may be sealed-in, they may also have the same shape throughout the whole length inside as well as outside the tube and also in the interior of the sealing member. It is thus possible to satisfy all the requirements which such tubes and devices have to comply with. In the first place the electrode system may be arranged in close proximity to the sealing member; furthermore the sealing member itself may be thin and finally the capacity of the constituent parts of the oscillatory circuit is the same throughout the whole length since the material and the shape may also be the same.

According to one embodiment of the invention, use is made of a triode wherein the grid rods and the anode are sealed as such into the sealing member and are continued to the exterior as constituent parts of the oscillatory circuit. In this case it is of importance that the possibility of sealing the whole circumference of the anode extended into the sealing member is attended with great advantages. If it is desired to have exactly the same capacity between the conductors inside and outside the tube, a: grid wire may be wound on the grid rods protruding from the tube. Substantially the same result may be obtained by slipping a metal cylinder on these rods. In order to simplify the construction of the tube, more particularly the manufacture thereof, it is also possible to seal the oathode directly into the sealing member. In this case all the constituent parts of the tube and an oscillatory circuit may be made and mounted beforehand, whereupon in a mould suitable for this purpose the sealing-in and, if desired, the connection with the bulb are effected in a single operation.

According to another embodiment of the present invention, the tube and the device are constructed in such manner that they may be utilized in push-pull. To that end the tube comprises two grids and two anodes which are arranged. on either side of the cathode. Furthermore the tube is closed at both ends by a member consisting of glass with cavities whilst at the one end the two grids and at the other end the two anodes are sealed-in and are continued as an oscillatory circuit.

According to a further form of construction, use is made of a discharge tube wherein the electrodes are present in reversed arrangement, that is to say that within the system there are one or more anodes which are surrounded by one or more grids which are surrounded in their turn b one or more cathodes. Owing to the fact that the constituent parts of the tube may be sealed-in in any desired thickness, the anode may be constituted by a comparatively thick rod or a hollow tube which can easily be cooled, is sealed, as are the supply conductors of the grid, directly into a sealin member and forms outside of the tube part of the oscillatory circuit. Owing to the fact that the cathode is on the outside, it is easy to obtain heavy currents whilst use can be made of comparatively low voltages, at least in comparison with tubes for generating high-frequency oscillations wherein the electrodes are mounted in the longitudinal direction of the tube as in the case of a cathode ray tube.

A tube in reversed arrangement as described hereinbefore may also be constructed as a multiple tube wherein a plurality of cathodes surround one or more grids and. anodes. The arrangement with which a plurality of cathodes surround a grid and an anode may more particularly be utilized if use is made of high-frequency polyphase supply.

The invention will be explained more fully with reference to the accompanying drawing which represents diagrammatically a device and a tube according to the present application. In this drawing l denotes the wall of a discharge tube inside of which are arranged a cathode 2, a grid 3 and an anode 4. At the lower end the tube is closed by a member 5 which consists of glass having small cavities as hereinbefore described and into which are sealed the electrodes or current supply conductors. The anode passes as such through the sealing member and forms at the exterior the part 6 of the oscillatory circuit. The other part 1 of the oscillatory circuit is formed by the directly continued rods of the grid, on to which, outside of the tube, a metal cylinder is slipped. Also the cathode is sealed-in as such and constitutes at the exterior a member 3. The tuning of the oscillatory circuit may be eiiected with the aid of a contact 9 which is constructed as a so-called tuning piston and may be displaced with the aid of a rod it, thus regulating the length of the oscillatory circuit and consequently the wave-length.

It is preferable that the member which closes the tube is arranged in a potential node of the oscillatory circuit in order to keep the dielectric losses in this circuit at a low value.

What we claim is:

1. An electric discharge tube having an envelope, a first electrode sealed in a portion of said envelope and extending therethrough and a second electrode, said sealed envelope portion comprising glass having a large number of finely divided cavities, said sealed envelope portion having a density less than 95% of the specific density of the lass thereof.

2. An electric discharge tube having an envelope, a first electrode and a cylindrical anode member sealed in a portion of said envelope, and surrounding said first electrode, said sealed envelope portion comprising glass having a large number of finely divided cavities, said portion having a density less than 95% of the specific density of the glass thereof.

3. A device for generating electrical oscillations comprising an electric discharge tube having an envelope, a unitary anode member sealed in a portion of said envelope and extending therethrough, a grid within said envelope and having supporting members sealed in and extending through said portion, said anode member and said grid supporting members forming an oscillatory circuit, said sealed envelope portion comprising glass having finely divided cavities, said portion having a density less than about 95% of the specific density of the glass of said portion.

EDUARD GERARDUS DORGELO. HENDRICUS JOHANNES LEMMENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

